The present invention relates to a crystalline polyesterpolyol obtainable from a polybasic carboxylic acid component and an aliphatic hydrocarbon diol component comprising 1,10-decanediol and/or 1,12-dodecanediol. The crystalline polyesterpolyol of the invention is capable of crosslinking with various crosslinking agents, and is useful for producing paints, adhesives, inks, and sealants.
The present invention also relates to a hot-melt adhesive comprising a crystalline polyesterpolyol having a number average molecular weight of 1,500 to 15,000 and obtainable from a polybasic carboxylic acid component and an aliphatic hydrocarbon diol component comprising 1,10-decanediol and/or 1,12-dodecanediol. The hot-melt adhesive of the invention necessitates an extremely short period of time for adhesion and is also excellent in adhesion strength, so that it can be used for various purposes as an adhesive.
Polyesters are well known compounds in the art and various polyesters are employed. In particular, polyesterpolyols are capable of crosslinking and curing with various crosslinking agents such as isocyanate compounds, and are widely used as paints, adhesives, inks, and sealants.
Among them, a crystalline polyesterpolyol has characteristics that it can be handled as a liquid having relatively low viscosity at a temperature of the melting point or higher and it solidifies within a short period of time through recrystallization when it is cooled at or below the crystallizing temperature in addition to its excellent mechanical properties. Owing to the characteristics, its use as components for reactive hot-melt adhesives and hot melt-type ink jet inks have been expanding.
Particularly, the market of the reactive hot-melt adhesives have been rapidly growing since they match social needs of lessening solvent and saving energy together with its excellent strength and adhering speed and high applicability to product lines in assembly industries. Furthermore, there is a strong demand for the enhancement of efficiency of continuous working, and therefore, a reactive hot-melt adhesive having more rapid setting rate is desired.
In order to meet the demand, combinations of a reactive hot-melt adhesive with an adhesive resin or a thermoplastic polymer have been examined. For example, European Patent Application Publication No. 0232055A describes a combination with an ethylene/vinyl acetate comonomer or a methylstyrene resin, and European Patent Publication No. 0246473A describes a combination with an acrylate oligomer. However, such reactive hot-melt adhesive contains a thermoplastic resin in high ratio even after the curing by crosslinking, so that the decrease of shear strength at high temperature cannot be avoided.
On the other hand, European Patent Application Publication No. 0248658A discloses a polyester-type hot-melt adhesive using an aromatic dicarboxylic acid. The use of an aromatic polyester improves the thermal resistance but there is a disadvantage that the viscosity at the melting is too high and therefore the workability at its application remarkably decreases.
Hitherto, as the raw materials used for the reactive hot-melt adhesives, terephthalic acid, isophthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, etc. are known as the polybasic carboxylic acid component, and ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, etc. as the diol component.
On the other hand, it is known, as described in Secchaku, vol. 28, No. 8, p. 5 (1984) and ADHESIVE AGE, p. 32, November (1987), that the crystallinity of a polyesterpolyol affects the setting rate. Namely, a polyesterpolyol having high crystallinity is extremely advantageous for accelerating the setting rate. Among the polyesterpolyols obtained from the above monomer combinations, Japanese Patent Laid-Open No. 88686/1990 discloses those wherein dodecanedioic acid and 1,6-hexanediol or sebacic acid and 1,6-hexanediol are used as raw materials for producing a reactive hot-melt adhesive having improved setting rate, a polyesterpolyol wherein dodecanedioic acid and ethylene glycol are used, and the like. However, it becomes difficult to satisfy the demand for further rapid setting with these combinations.
An object of the invention is to provide a crystalline polyesterpolyol producible from easily available raw materials, capable of rapid setting and rapid drying as a component of adhesives, paints and inks, and imparting sufficient adhesion strength.
Another object of the invention is to provide a hot-melt adhesive producible from easily available raw materials, capable of rapid setting and rapid drying, and imparting sufficient adhesion strength.
As a result of extensive studies for solving the above problems, the present inventors have found that a polyesterpolyol, obtainable from a polybasic carboxylic acid component and an aliphatic hydrocarbon diol component, wherein an aliphatic hydrocarbon diol component comprising 1,10-decanediol and/or 1,12-dodecanediol is used and a number average molecular weight is from 1,500 to 15,000 becomes a crystalline polyesterpolyol. Accordingly, they have reached the present invention.
The present inventors further have found out a hot-melt adhesive comprising the crystalline polyesterpolyol, and therefore, have reached the present invention.
The following will explain the invention in detail.
The aliphatic hydrocarbon diol component to be used in the invention comprises 1,10-decanediol and 1,12-dodecanediol. Preferred is 1,12-dodecanediol. These are used solely or as a mixture. Furthermore, they can be mixed with an aliphatic hydrocarbon diol component having carbon atoms less than that of 1,10-decanediol. The amount of 1,10-decanediol or 1,12-dodecanediol to be used at that time is not particularly limited but, in the case of obtaining a crystalline polyesterpolyol, the amount is 1 mol % or more, preferably 5 mol % or more, more preferably 20 mol % or more of the total aliphatic hydrocarbon diol component. In particular, at the amount of 20 mol % or more, a high crystalline polyesterpolyol is obtained.
The polybasic carboxylic acid component to be used in the invention includes an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid, and includes an aliphatic dicarboxylic acid having 2 to 12 carbon atoms and an aromatic dicarboxylic acid. Preferred is an aliphatic dicarboxylic acid having 2 to 12 carbon atoms, and more preferred is an aliphatic dicarboxylic acid having 2 to 6 carbon atoms. Concrete examples include oxalic acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, isophthalic acid, terephthalic acid, and the like. Preferred are oxalic acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid. These may be used solely or as a mixture.
The polyesterpolyol according to the invention can be obtained by subjecting the above-described aliphatic hydrocarbon diol component and the polybasic carboxylic acid component to known dehydrative polycondensation. Usually, the equivalent ratio of the hydroxyl group of the aliphatic hydrocarbon diol component and the carboxyl group of the polybasic carboxylic acid component (hydroxyl group/carboxyl group) is preferably from 1.02 to 1.5, more preferably from 1.05 to 1.3. Concretely, the esterification is carried out by subjecting the predetermined amount of the aliphatic hydrocarbon diol component and the polybasic carboxylic acid component to dehydrative polycondensation in the presence or absence of a catalyst at a temperature range of 150 to 250xc2x0 C. for about 3 to 20 hours.
As the catalyst, it is preferable to carry out the reaction in the presence of a titanium catalyst such as titanium tetrabutoxide or a tin catalyst such as dibutyltin oxide owing to its acceleration of the dehydrative polycondensation. The catalyst may be charged together with the diol component and the polybasic carboxylic acid component, or may be added after the proceeding of pre-polymerization in the absence of any catalyst. At the production of the polyesterpolyol, it is desirable to carry out the production so that its both ends become almost hydroxyl groups and no terminal carboxyl group is formed. For this purpose, it is particularly effective and thus preferable to add the above-described catalyst after the pre-polymerization.
The number average molecular weight of the polyesterpolyol obtainable from a polybasic carboxylic acid component and an aliphatic hydrocarbon diol component comprising 1,10-decanediol and/or 1,12-dodecanediol is from 1,500 to 15,000, preferably from 2,000 to 10,000, more preferably from 3,000 to 8,000. When the molecular weight is less than the range, thermal resistance, chemical resistance and strength at setting are not sufficient. When it is larger than the range, the viscosity at the melting becomes high and therefore the handling becomes difficult.
The crystallinity in the invention is evaluated only by the measurement of crystallinity according to X-ray diffraction method (Ruland method) of the polyesterpolyol solidified from the melted state under cooling at a rate of 10xc2x0 C./minute. Usually, the crystallinity of 40% or more is sufficient. In the case of particularly aiming at a high crystalline polyesterpolyol, the one having the crystallinity of 50% or more is preferable. The polyesterpolyol having the crystallinity of 50% to 70% is more preferable.
The polyesterpolyol to be used in the invention is a crystalline polyesterpolyol having a number average molecular weight of 1,500 to 15,000, and obtainable from a polybasic carboxylic acid component and an aliphatic hydrocarbon diol component comprising 1,10-decanediol and/or 1,12-dodecanediol. These may be used solely or as a mixture without problem.
Moreover, the polyesterpolyol may be used in combination with other polyesterpolyol. In this case, the amount of the crystalline polyesterpolyol of the invention is 0.1 wt % or more, preferably 0.5 wt % or more.
The polyisocyanate to be used in the hot-melt adhesive of the invention includes usually well-known aromatic, aliphatic and cyclic diisocyantes or highly functional or polymeric polyisocyanates. Concrete examples include 1,5-naphthylene diisocyanate, 4,4xe2x80x2-diphenylmethane diisocyanate, 4,4xe2x80x2-diphenyldimethylmethane diisocyanate, 4,4xe2x80x2-dibenzyl diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene duisocyanate, 2,2,4-trimethylhexamethylene diusocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4xe2x80x2-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, and derivatives thereof.
The ratio of the polyesterpolyol and the polyisocyanate to be used is not particularly limited, and they can be used within a usual range. Namely, the molar ratio of the OH group of the polyesterpolyol to the NCO group of the polyisocyanate is from 1:1.2 to 1:3.0, preferably 1:1.5 to 1:2.5. The reaction conditions are also not particularly limited and the reaction is carried out under the usual conditions, concretely, at a temperature range of 50 to 150xc2x0 C. for 1 to 5 hours. Also, the reaction may be carried out in a solvent.
The viscosity of the hot-melt adhesive obtainable according to the invention is 100,000 cps or less, preferably 1,000 to 50,000 cps, more preferably 3,000 to 40,000 cps at 120xc2x0 C.
The hot-melt adhesive of the invention may be used as it is, and also may be used after the addition of a plasticizer, a thermoplastic polymer, a tackifier, a filler, an antioxidant, and the like which are employed for usual hot-melt adhesives.
The hot-melt adhesive obtainable according to the invention is suitable for adhesion step at continuous working process owing to its short period of time required for adhesion. For example, shoemaking industry, lumber-processing industry, paper-manufacturing industry, metal industry, resin-processing industry may be mentioned.